Aesop's Fables, translated by Laura Gibbs (2002)

They say that hyenas change their nature every year, so that sometimes
they are male and sometimes female. So when a hyena saw a fox and criticized
her for having spurned her friendly overtures, the fox replied, 'Don't
blame me! Blame your own nature, which makes it impossible for me to tell
whether you would be my girlfriend or my boyfriend!' This is a story for an ambiguous person.